The cortistatins are a group of anti-angiogenic steroidal alkaloids first isolated in 2006 from the marine sponge Corticium simplex. See, e.g., Aoki, et al., JACS (2006) 128: 3148-9. From the date of isolation to the present, these natural products have been the subject of much study, especially in the development of total syntheses and of new unnatural biologically active analogs. See, e.g., Aoki et al., Bioorganic & Medicinal Chemistry (2007) 15: 6758-62. Mousseau et al., Cell Host & Microbe (2012) 12: 97-108; Chen et al., Organic & Biomolecular Chemistry (2010) 8: 2900; Hardin et al., European Journal of Organic Chemistry (2010) 19: 3553. Thus, there is an active interest in the development of new cortistatin analogs and methods of their preparation.
U.S. Pat. No. 9,127,019 titled “Cortistatin Analogs and Synthesis Thereof” filed by Flyer, et. al., and assigned to the President and Fellows of Harvard College describes analogs of Cortistatins A, J, K, and L having the general Formula I and salts thereof, and the synthesis thereof, wherein R1, R2, R3, R4, n, and m are as described therein.

The '019 patent discloses that such compounds are anti-angiogenic and can be used to treat proliferative diseases.
WO 2015/100420 titled “Cortistatin Analogs and Syntheses and Uses Thereof” filed by Shair, et al., and also assigned to the President and Fellows of Harvard College describes further analogs of Cortistatin and methods and compositions that include the described cortistatin analogs to treat proliferative disorders such as cancer, and in particular, a hematopoietic cancer such as leukemia, multiple myeloma (MM), acute myelocytic leukemia (AML), a myeloproliferative neoplasm, acute lymphoblastic leukemia (ALL), chronic myeolcytic leukemia (CML) and primary myelofibrosis (PMF). More generally, the '420 application describes a method to treat a condition associated with CDK8 and/or CDK19 kinase activity, that includes administering an effective amount of a disclosed compound or its pharmaceutically acceptable salt, quaternary amine, or N-oxide. CDK8 and its regulatory subunit cyclin C are components of the RNA polymerase II haloenyme complex, which phosphorylates the carboxy-terminal of the largest subunit of RNA polymerase II. CDK8 regulates transcription by targeting the CDK7/cyclin H subunits of the general transcription factor TFIIH.
Other synthetic and biological descriptions of Cortistatin A and analogs of Cortistatin A have been described in: Chiu et al., Chemistry (2015), 21: 14287-14291, titled “Formal Total Synthesis of (+)-Cortistatins A and J”; Valente et al., Current HIV Research (2015), 13: 64-79, titled “Didehydro-Cortistatin A Inhibits HIV-1 Tat Mediated Neuroinflammation and Prevents Potentiation of Cocaine Reward in Tat Transgenic Mice”; Motomasa et al., Chemical & Pharma. Bulletin (2013), 61: 1024-1029 titled “Synthetic Studies of Cortistatin A Analog from the CD-ring Fragment of Vitamin D2”; Valente et al., Cell Host & Microbe (2012), 12: 97-108 titled “An Analog of the Natural Steroidal Alkaloid Cortistatin A Potently Suppress Tat-dependent HIV Transcription”; Motomasa et al., ACS Med. Chem. Lett. (2012), 3: 673-677 titled “Creation of Readily Accessible and Orally Active Analog of Cortistatin A”; Danishefsky et al., Tetrahedron (2011) 67: 10249-10260 titled “Synthetic Studies Toward (+)-Cortistatin A”; Motomasa et al., Heterocycles (2011), 83: 1535-1552, titled “Synthetic Study of Carbocyclic Core of Cortistatin A, an Anti-angiogenic Steroidal Alkaloid from Marine Sponge”; Motomasa et al., Org. Lett. (2011), 13: 3514-3517, titled “Stereoselective Synthesis of Core Structure of Cortistatin A”; Baran et al., JACS (2011), 133: 8014-8027, titled “Scalable Synthesis of Cortistatin A and Related Structures”; Hirama et al., JOC (2011), 76: 2408-2425, titled “Total Synthesis of Cortistatins A and J”; Zhai et al., Org. Lett. (2010), 22: 5135-5137, titled “Concise Synthesis of the Oxapentacyclic Core of Cortistatin A”; Stoltz et al., Org. Biomol. Chem. (2010), 13: 2915-2917, titled “Efforts Toward Rapid Construction of the Cortistatin A Carbocyclic Core via Enyne-ene Metathesis”; Sarpong et al., Tetrahedron (2010), 66: 4696-4700, titled “Formal Total Synthesis of (+)-Cortistatin A”; Nicolaou et al., Angewandte Chemie (2009), 48: 8952-8957, titled “Cortistatin A is a High-Affinity Ligand of Protein Kinases ROCK, CDK8, and CDK11”.
U.S. Patent Application Publication US2013/0217014 and PCT Application WO2013/122609 titled “Methods of Using CDK8 Antagonists” filed by Firestein, et al., and assigned to Genentech, describes the use of CDK8 antagonists against various cancers.
Despite the progress to date, it would be advantageous to provide new compounds that can be used to treat such disorders in a host, including a human.